A thirstbuster run is when one or multiple people at usually late / random hours get the sudden urge to travel to the circle-K convenience store and buy and consume thirstbusters, cheap 44 ounce sodas.

12:00 A.M, two people zoned out on the couch.
Person 1:"I'm in the mood for a thirstbuster, wanna make a thirstbuster run?"
Person 2:"Sure"